A cross‐sectional study of community‐level physician retention and hospitalization in rural Ontario, Canada

Abstract Purpose Many rural communities experience poor family physician retention. We examined the association between community‐level physician retention and hospitalization for all causes and ambulatory care‐sensitive conditions (ACSCs) in 2017 among residents of rural communities in Ontario, Canada. Methods We conducted a population‐based cross‐sectional study by linking administrative data from the public health insurance program in Ontario. To create the physician retention measure for each rural community, we divided the number of family physicians who worked in the community in both 2016 and 2017 by the total number of unique family physicians in the community in either year. We grouped retention level by tertile and added a fourth category, “no physician” to include communities that did not have any residing physicians in either 2016 or 2017. Outcomes were all‐cause hospitalization and ACSC hospitalization between April 1, 2017 and March 31, 2018. Findings Among 1,436,794 rural residents, there were 93,752 all‐cause hospitalizations and 8,691 ACSC hospitalizations in 2017. After controlling for other predictors, compared to residents in low‐retention communities, residents of medium‐ and high‐retention communities were 0.888 (95% CI: 0.868‐0.909) and 0.937 (95% CI: 0.915‐0.960) times as likely to have all‐cause hospitalization, and residents of high‐retention communities were 0.918 (95% CI: 0.858‐0.981) times as likely to have ACSC hospitalization in 2017. Conclusions Community‐level physician retention is significantly associated with all cause and ACSC hospitalization in rural communities in Ontario, and may serve as an alternate measure to assess the impact of disrupted continuity of care.

High continuity of care has been shown to improve the quality of primary health care. 11,12 Researchers have constructed a number of metrics to measure continuity of care using administrative fee-for-service billing data, including the Usual Provider Continuity Index and Concentration of Care Index. [12][13][14][15] However, in many rural communities in Canada, family physicians are paid by alternate payment plans and may not submit shadow billings. As a result, these traditional metrics of continuity of care cannot be used to research the quality of primary health care in rural communities.
Measuring physician retention offers a potential alternative. 10 This study will examine the association between physician retention and hospitalization for all causes and ambulatory care-sensitive conditions (ACSCs) over a 1-year period among residents of rural communities in Ontario that are outside the commuting zones of larger urban centers, and with less than 10,000 population. Also known as preventable hospitalizations, ACSC hospitalizations are an indicator of poor primary health care and are defined as hospitalizations for any of the following 7 conditions: angina, asthma, congestive heart failure (CHF) and pulmonary edema, chronic obstructive pulmonary disease (COPD), diabetes, grand mal seizures, and other epileptic seizures and hypertension. 12 All cause and ACSC hospitalization have been shown to vary with established measures of continuity of care. 12,14,15 We hypothesize that residents of rural communities with low physician retention will have a greater likelihood of being hospitalized for all cause and ACSC hospitalization in a 1-year period than residents of rural communities with high physician retention, but a lower likelihood of all cause and ACSC hospitalization than communities with no residing physician. This initial, exploratory study will assess whether community-level physician retention serves as an alternate measure of access and continuity of care in rural communities.

METHODS
We conducted a population-based cross-sectional study using linked health administrative data held at ICES, an independent, nonprofit research institute funded by an annual grant from the Ontario Ministry of Health and the Ministry of Long-Term Care. As a prescribed entity under Ontario's privacy legislation, ICES is authorized to collect and use health care data for the purposes of health system analysis, evaluation, and decision support. Secure access to these data is governed by policies and procedures that are approved by the Information and Privacy Commissioner of Ontario. The use of the data in this project is authorized under section 45 of Ontario's Personal Health Information Protection Act and does not require review by a Research Ethics Board.
We linked demographic information on individuals covered by the Ontario Health Insurance Program (OHIP) (public, universal health insurance program for medically necessary physician and hospital health services), with physician billings, hospitalizations, emergency room visits, practicing physicians, medical practice organizations, and geographic data from the national census. These datasets were linked using unique encoded identifiers and analyzed at ICES. We included individuals covered by OHIP as of April 1, 2017. We excluded individuals who had missing or invalid age or sex data; died on or before April 1, 2017; were not residents of Ontario; were missing postal codes, census subdivision, or Local Health Integration Network (LHIN) regional data; had no record of contact with the health system for at least 7 years and were not eligible for OHIP. Urban residents were then excluded to create a cohort of residents living in rural census subdivisions (ie, communities). Rural census subdivisions are small towns and rural communities outside the commuting zones of larger urban centers, and with less than 10,000 population. We included only communities with less than 5% of its population working in larger communities (based on Statistics Canada's metropolitan influenced zones measure) 16 to limit the likelihood that rural residents were accessing care outside their home community. This definition of rural is recommended by Statistics Canada 16 and has been used in other studies of rural health care in Canada. 3 For each rural community, we divided the number of physicians who worked in the community in both 2016 and 2017 by the total number of unique physicians in the community in either year. We grouped retention level by tertile (where high retention was 83.34%-100%, moderate retention was 66.68%-83.33%, and low retention was 0.1%-66.67%).
The cutoffs were based on the number of communities in each group, and consensus among authors that these cutoffs were consistent with general experience (ie, 5 of 6 physicians remained in the same community from 1 year to the next was considered good retention). In addition, we created a fourth category, "no physician" to include communities that did not have any physician whose main address was in the community in either 2016 or 2017.
Outcomes were all-cause hospitalization (yes/no) and ACSC hospi- Covariates included patient, community, and health service variables. Patient-level covariates were age, sex, and number of comorbidities; patient age and sex were identified in the RPDB. The number of comorbidities was based on the presence of any of asthma, CHF, COPD, diabetes, hypertension, dementia, human immunodeficiency virus (HIV), rheumatoid arthritis, or Crohn's/colitis. Individuals with these comorbidities were identified from databases (Ontario asthma database, CHF database, COPD database, Ontario diabetes dataset, Ontario hypertension dataset, Ontario HIV database, Ontario rheumatoid arthritis dataset, and Ontario Crohn's and colitis cohort dataset) of validated condition-specific cohorts that were developed by ICES using hospitalization, physician billing, emergency department, and same day surgery data. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] The community-level variables were defined as physicians per 1,000 population in the community.
Health service variables were the type of primary care organization to which the patient belonged, and number of primary care, specialist, and emergency department visits between April 1, 2017 and March 31, 2018. Primary care organization describes different practice and funding models introduced in Ontario as part of a series of primary care reforms. 33,34 Most physicians belong to organizations that are patient enrollment models and have a defined roster of patients. As part of enrollment with a physician, patients agree not to seek care All analyses were conducted using SAS version 9.4 (SAS Institute, Cary, NC). After describing the characteristics of the sample, we used ANOVA or chi-square tests to compare the characteristics of residents who lived in communities with different levels of physician retention.
We used Pearson r correlation and variable inflation factor tests to assess multicollinearity between variables a priori. We used univariable and multivariable logistic regression to examine the relationship between each predictor and each outcome. Multivariable regression adjusted for other significant covariates and age-sex interaction, which was identified through the bivariate analyses. The final multivariate regression model includes only statistically significant predictors and interaction terms.
In sensitivity analyses, we excluded communities in the northernmost health regions (referred to as LHIN at the time of the study) and repeated our analyses. These regions of the province have a high proportion of Indigenous people who live in remote and isolated areas and have health services delivery and governance that differ from communities in the rest of the province. We also repeated our analysis of ACSC hospitalization to adults 18-74 years, consistent with more restricted definitions of ACSC. 12,14

RESULTS
After applying inclusion and exclusion criteria (   In sensitivity analyses with the sample restricted to non-northern rural communities, or ages 18-74 in all rural communities, similar results were obtained (Tables 5 and 6). When the sample for ACSC hospitalization is restricted to those that are 18-74 years old, community-level physician retention was not a significant predictor of ACSC hospitalization.
In all multivariate regressions, the likelihood of all-cause hospitalization or ACSC hospitalization did not differ between residents of communities with no doctor and residents of communities with low retention.

DISCUSSION
We found that community-level physician retention is a significant predictor of all-cause hospitalization and ACSC hospitalization in rural communities in Ontario. These results are consistent with findings from an earlier study in another Canadian province. 10 In our analyses,

Limitations
We used a 1-year cross-sectional design. While a cross-sectional design ensures that the outcome (hospitalization) and exposure (physician retention) occur in the same time period, they produce correlational rather than causal associations. Moreover, physician retention metrics based on 1 year of data may not capture longer term trends in physician retention. Future studies should examine a longer exposure to generate more stable estimates of retention and avoid mis-labeling a community. While physician retention is calculated at the community level, individual residents in a low-retention community may enjoy high continuity of care if their own physician remains in the community. Further research is needed to disentangle the effect of continuity with a single provider from the effects of community-level physician retention. Our study used administrative health data, which do not capture many confounding variables that may contribute to hospitalization. Moreover, administrative health data do not capture services provided by nurses or other health care providers. These data are needed to capture the full-range of health services, especially those provided in "no-doctor" communities.

CONCLUSIONS
Community-level physician retention is significantly associated with all cause and ACSC hospitalization in rural communities in Ontario. Rural communities with medium or high physician retention had better outcomes than communities with low retention or no doctors. This initial study shows that community-level physician retention is a promising measure of continuity appropriate for use in rural communities. Further research examining a wider range of health outcomes and including measures of physician retention over longer periods of time is needed to provide more robust evidence to inform health service policy in rural communities.

ACKNOWLEDGMENTS
Parts of this material are based on data and/or information compiled and provided by CIHI. However, the analyses, conclusions, opinions, and statements expressed in the material are those of the author(s), and not necessarily those of CIHI.

FUNDING SOURCES
This study was supported by ICES, which is funded by an annual grant

DISCLOSURES
None to declare.